The first fifteen minutes did not seem very promising, like those movies depicting troubled teens in a spiral of decadence and irreparability, but... things picked-up with realistic performances and good empathy between the characters. Very likeable family in the end, with no traces of a maternal figure, you can only praise the kids' character and judgement all those years, without the vigilance of parents.
Amazing work. It take you right into the merciless changes happening in China, sweeping any concept of graduality you may have. This country, as in the many "countries" that integrate it, are defying our standards every single day, for good and for bad, it is just happening.